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ARRL Propagation Bulletin ARLP018 (2006)

ARLP018 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 18  ARLP018
From Tad Cook, K7RA
Seattle, WA  May 5, 2006
To all radio amateurs 

ARLP018 Propagation de K7RA

This was a nice, quiet week with no notable geomagnetic activity.
In fact, the middle latitude K index was 0 for a 36-hour period
centered on April 30, and around the same time the high latitude
college K index was 0 for 51 continuous hours. Average daily sunspot
numbers were nearly double the previous seven days, rising over 29
points to 59.7.

As this bulletin is being written early Friday morning, the IMF is
pointing south, leaving Earth vulnerable to solar wind. The
planetary A index reached 5 on Thursday, May 4, and over the weekend
is predicted at 20, 30, 20 and 12 for May 5-8. Geophysical Institute
Prague gives a forecast until May 11 of active geomagnetic
conditions on May 5 and 6, unsettled May 7, quiet to unsettled May
8, quiet on May 9, back to unsettled on May 10, and unsettled to
active on May 11.

April has ended, so this is a good time to look at average monthly
sunspot numbers and solar flux for the past year.

The average daily sunspot numbers for the months April 2005 through
April 2006 were 41.5, 65.4, 59.8, 68.7, 65.6, 39.2, 13, 32.2, 62.6,
26.7, 5.3, 21.3 and 55.2. Average daily solar flux for the same
months was 85.9, 99.5, 93.7, 96.5, 92.4, 91.9, 76.6, 86.3, 90.8,
83.4, 76.5, 75.5 and 88.9.

Paul Peters, VE7BZ of Cobble Hill, British Columbia wrote in to say
that conditions around those quiet days last week were fantastic.
"On April 29, 30 and May 1, the 20 meter band conditions to Europe
were almost unbelievable they were so good. On April 29 and 30, I
called CQ once at 0300z and four hours later at 0700z I was still
working down an endless pileup. Normally for us--living this far
north--20m phone is usually dead in our evenings, but such was not
the case recently. These were great nights!"

Cobble Hill is toward the southern end of Vancouver Island, just
north of Victoria, and about 50 miles southwest of the city of

Richard Vincent, HS0ZFQ (he is KR7R when in the United States)
retired from the postal service in Seattle and now lives in Chiang
Rai in the far north of Thailand, between the borders with Laos and
Myanmar (Burma). Over those same days at the end of April that VE7BZ
wrote about, Richard wrote, "I was hearing stateside signals all
over the place on 20 meter SSB starting about 1300z, which is 8:00
PM local time. From this end VR2XMT, Charlie Ho in Hong Kong was
running USA stations and so were a couple of the Russian big guns. I
had not heard conditions like that since I got on the air here last

Richard currently uses a dipole, and has plans to soon put up a

Last week's bulletin mentioned Greg Andracke, W2BEE of Pine Plains,
in upstate New York, and his experience working Chagos on 30 meters
early on a Saturday morning in mid-April. Several people wrote in to
say that this was a normal time to work Chagos via the long path on
that band. Actually, that is true for many other places in North
America, but not where Greg is, in the Northeast.

The people we heard from were all south and west of Greg, although
checking a propagation prediction program shows that the Southeast
United States should have a good path as well. Southern California
around that time on that date would have a very good short path
opening to Chagos.

Dale Tongue, AC7NP, currently in El Paso, Texas wrote in to ask
about sunspot graphs, and where he could find them on the web. For a
graph of the last year of sunspots, check, Also see all recorded sunspot
cycles back to 1749 at,

A graph of the current sunspot cycle is at,, and you can compare recent
cycles at,

You can see for a chart of the past few
months, and check out the links lower on the page for interesting
historical data.

And finally, Thomas Giella, KN4LF of Lakeland, Florida notes that he
has started a new email listserver for radio propagation. See info
on subscribing at,

If you would like to make a comment or have a tip for our readers,
email the author at,

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin, see the ARRL Technical
Information Service propagation page at, An archive of past
propagation bulletins is at,

Sunspot numbers for April 27 through May 3 were 63, 68, 64, 62, 51,
58 and 52 with a mean of 59.7. 10.7 cm flux was 100.7, 100.1, 101.2,
99.9, 93.4, 89.4, and 89, with a mean of 96.2. Estimated planetary A
indices were 5, 12, 3, 1, 2, 4 and 3 with a mean of 4.3. Estimated
mid-latitude A indices were 3, 10, 2, 0, 2, 4 and 2, with a mean of


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